 Okay, in this module, we will be discussing that esophageal in vertebrates. Esophagus is the singular esophageal plural. That is, in most of the vertebrates, it is esophageal. The esophagus, first we will see what it is. It is a muscular tube that connects throat, that is, the pharynx with the stomach. So, depending upon the type of the animal, its length is in the mucleus. And this esophagus, it is lined, mucous membrane lines inside you. And it produces mucous membrane, mucous. And esophagus runs behind the windpipe. And on its back side, they run in fact, they run parallel to each other. And in other animals as well. In fissures and amphibians, the esophagus is short because of the absence of the neck. Now, in amniotes, the esophagus is much longer due to their longer necks. As you can see, there are many birds. We will talk about them in detail. We will look at their diagrams and photographs. So, obviously, their esophagus is a long tube. Because it has to be connected to the mouth, to the body or to the stomach. That is through a long tube. So, that is called as mucous, that is called as esophagus. Birds, particularly grain and seed eaters, because there is a variety of birds. They are called grain eaters. They are called seed eaters. So, depending upon the food of the bird, this is called as mucous. The esophagus that has a crop that develops from the caudal portion of the esophagus. The caudal portion of the esophagus is dilated, which is called as crop. Now, a bird's crop is an expandable muscular pouch near the gullet or throat. It is used to store excess food for later digestion. As you must have seen in our observation, when the gullet, the animals, the birds, especially the hen, when they eat a lot of food, its neck, where it ends, if we feel it from our hands, we feel that all the grains are in its pouch, in its bag. That is called as crop. So, storing food in the crop ensures an almost continuous supply of food to the stomach and intestine for digestion. So, it eats the food very quickly. It stores there, then from there, slowly, slowly. With mucous, it becomes slippery. Then it starts moving into the next part of the digestive system. Now, this structure allows these birds to reduce the frequency of feeding. So, instead of eating the bird at all times, it eats a lot of food in a short time, and then it stores the birds. Now, birds that have more visible crop include, which is very clear. As you can see from the outside, they are vultures, hawks, falcons, eagles, gulls, and many types of quail, including even hen, a domestic animal. In this diagram, we are seeing that these are the vultures, and these are the crops, which are very evident. This is the hen, and this is the esophagus. So, this is the tube, which is the esophagus, and then this is the crop. The food comes directly from here. And then, after slipping from there, that moves into the gizzard. And the gizzard is usually, as you can see here, when we buy a poultry or a meat, it also gives a pot. So, in that pot, this is a very muscular part, where these birds, especially the wild birds, also eat conker, so that it works as a crushing. And from there, then this food, partly, that is broken food, that moves into intestine, and then further process of digestion happens in it. This is all about the esophageal in the vertebrates.